This invention relates to a scroll type compressor, and particularly relates to measures against reduction of its operating efficiency.
As compressors for compressing refrigerant in a refrigeration cycle, there have been conventionally used scroll type compressors disclosed for example in Japanese Unexamined Patent Publication No. 5-312156. The scroll type compressor is provided in its casing with a fixed scroll and a movable scroll which have respective volute laps meshed with each other. The fixed scroll is fixed to the casing, and the movable scroll is coupled to an offset shaft portion of a drive shaft. Further, the scroll type compressor is arranged so that the movable scroll does not rotates on the axis of the fixed scroll but travels bodily around the fixed scroll to contract a compression space defined between both the laps thereby compressing refrigerant.
Meanwhile, as shown in FIG. 14, compressing the refrigerant causes the movable scroll (OS) to experience a thrust load PS as an axial force and a radial load PT as a lateral force. Therefore, in an arrangement wherein a high-pressure section (P) is provided for making a high refrigerant pressure PA act on the back face (bottom face) of the movable scroll (OS) to press the movable scroll (OS) against the fixed scroll (FS) with a force counteracting the axial force PS, if the pressing force is small and a vector as the resultant of forces acting on the movable scroll (OS) passes outside of the outer periphery of a thrust bearing, the movable scroll (OS) will be inclined (upset) as being shown in FIG. 15 by the action of so-called upsetting moment M. This induces leakage of the refrigerant, resulting in decreased efficiency. On the other hand, in the arrangement wherein the movable scroll (OS) is pressed against the fixed scroll (FS) with the force counteracting the axial force PS as shown in FIG. 14, if the pressing force is contrariwise large (and a vector as the resultant of forces acting on the movable scroll (OS) passes inside of the outer periphery of the thrust bearing), it will be possible to prevent the movable scroll (OS) from upsetting.
In the meantime, the scroll type compressor has a constant volume ratio. Therefore, as shown in FIG. 16, even if the operating conditions change so that a high pressure or a low pressure varies to change the compression ratio, the axial force PS and the lateral force PT do not largely change. In contrast, the pressing force from the above-mentioned refrigerant pressure (referred to as a back pressure in the figure) on the back face of the movable scroll (OS) changes to a large extent with the change in the compression ratio.
Here, if the area of the high-pressure section (P) which makes a high pressure act on the movable scroll (OS) is set so as not to upset the movable scroll (OS) under conditions of high compression ratios as shown in FIG. 17A, the movable scroll (OS) will be easily upset under conditions of low compression ratios because of lack of the pressing force, for example, due to a reduced high pressure.
On the other hand, if the area of the high-pressure section (P) is set in conformity with the conditions of low compression ratios, a high compression ratio induced for example by an increase in the high pressure will cause the pressing force of the movable scroll (OS) against the fixed scroll (FS) to be excessive relative to a minimum pressing force determined by the axial force PS and the lateral force PT as shown in FIG. 17B. As a result, a significant thrust force upward when viewed in FIG. 14 acts on the movable scroll (OS) so that mechanical loss will be increased to reduce the efficiency.
The above is substantially the case for the variation in the low pressure (which usually varies together with the high pressure). Accordingly, generally speaking, in scroll compressors of the type which uses a refrigerant pressure or the like to press the movable scroll (OS) against the fixed scroll (FS), upset of the movable scroll tends to easily occur at lower compression ratios with reference to a compression ratio substantially specific for each compressor while the pressing force tends to easily become excessive at higher compression ratios.
The present invention has been devised in view of such problems, and an object thereof is to prevent decrease in efficiency by controlling the pressing force of the movable scroll against the fixed scroll.
The present invention provides for controlling a pressing force of a movable scroll (22) against a fixed scroll (21) depending upon operating conditions in a manner to change the pressing force in accordance with the variation in the compression ratio.
Specifically, a solution taken in the present invention is predicated upon a scroll type compressor including: a fixed scroll (21) fixed inside of a casing (10); a movable scroll (22) meshed with the fixed scroll (21); and pressing means (40) for pressing the movable scroll (22) against the fixed scroll (21). Further, the pressing means (40) is arranged to control a pressing force of the movable scroll (22) against the fixed scroll (21) in accordance with variation in compression ratio. Thus, the pressing force can be suppressed at high compression ratios while the suppression can be relieved at low compression ratios, thereby providing control of the pressing force depending upon operating conditions. It is to be noted that the manner to control the pressing force in accordance with the variation in the compression ratio can include using, for example, a pressure differential between high and low pressures or the high pressure (a discharge pressure).
In the above construction, for example, the pressing means (40) can be arranged to have a high-pressure space (S2) that serves a back face side of the movable scroll (22) and to suppress the pressing force of the movable scroll (22) against the fixed scroll (21) when the compression ratio exceeds a predetermined value (i.e., when the movable scroll (22) comes into a condition to be pressed with a sufficient force against the fixed scroll (21)). It is to be noted that, in this case, as the working condition that xe2x80x9cthe compression ratio exceeds a predetermined valuexe2x80x9d, use can be made of approximate conditions such as whether the pressure differential between high and low pressures has reached a preset given value (this is also the case for the following respective arrangements).
Further, in the above arrangement, the pressing means (40) can have a structure that includes an oil groove (43) formed between contact surfaces of the fixed scroll (21) and the movable scroll (22) in contact with each other and high-pressure oil introducing means (46) for introducing a high-pressure oil into the oil groove (43) when the compression ratio exceeds the predetermined value.
Furthermore, in the above arrangement, the highpressure space (S2) is preferably a high-pressure oil working space into which the high-pressure oil is supplied, and the high-pressure oil introducing means (46) is preferably arranged to guide the high-pressure oil in the high-pressure oil working space (S2) into the oil groove (43) when the compression ratio exceeds the predetermined value.
Moreover, in the above arrangement, the high-pressure oil introducing means (46) preferably has a structure that includes a high-pressure oil introduction passage (44) communicating from the high-pressure oil working space (S2) to the oil groove (43) and a high-pressure oil introduction valve (45) for opening/closing the high-pressure oil introduction passage (44).
Further, in the above arrangement, the high-pressure oil introduction valve (45) is preferably arranged to open the high-pressure oil introduction passage (44) upon excess of the compression ratio over the predetermined value while closing the high-pressure oil introduction passage (44) at the compression ratio equal to or less than the predetermined value.
Furthermore, in the above arrangement, the high-pressure oil introduction valve (45) can have a structure that includes a cylinder (47) disposed to traverse the way of the high-pressure oil introduction passage (44) and a piston-like valve body (48) provided for reciprocation movement in the cylinder (47), and the valve body (48) can be arranged to move to an open position at which the high-pressure oil introduction passage (44) is opened upon excess of the compression ratio over the predetermined value while moving to a closed position at which the high-pressure oil introduction passage (44) is closed at the compression ratio equal to or less than the predetermined value.
Moreover, in the above arrangement, the cylinder (47) of the high-pressure oil introduction valve (45) can have a structure that communicates at one end thereof with a low-pressure space (S1) provided in the casing (10) and communicates at the other end with a high-pressure space (S3) in the casing (10), urging means (50) can be provided for urging the valve body (48) toward the closed position in the cylinder (47), and an urging force of the urging means (50) can be set in accordance with a predetermined pressure differential between the low-pressure space (S1) and the high-pressure space (S3) so that the urging means (50) holds the valve body (48) at the closed position when the compression ratio is equal to or less than the predetermined value and allows movement of the valve body (48) to the open position when the compression ratio exceeds the predetermined value.
Further, in the above arrangement, the valve body (48) can have a structure that includes a communication passage (48a) to block the high-pressure oil introduction passage (44) at its closed position while opening the high-pressure oil introduction passage (44) through the communication passage (48a) at its open position.
In this structure, the communication passage (48a) of the valve body (48) is preferably constituted by a circumferential channel formed in an outer peripheral surface of the valve body (48).
Further, in the above arrangement, a frame (23) for separating the low-pressure space (S1) and the high-pressure space (S3) can be disposed in the casing (10) below the movable scroll (22), a sealing member (42) can be provided for dividing a space located between the frame (23) and the movable scroll (22) into the low-pressure space (S1) and the high-pressure oil working space (S2), and the frame (23) can be provided with the high-pressure oil introduction passage (44) and the high-pressure oil introduction valve (45).
Further, another solution taken in the present invention is also predicated upon the above-mentioned scroll type compressor including: a fixed scroll (21) fixed inside of a casing (10); a movable scroll (22) meshed with the fixed scroll (21); and pressing means (40) for pressing the movable scroll (22) against the fixed scroll (21). Further, the pressing means (40) can also be arranged to have a high-pressure space (S2) that serves a back face side of the movable scroll (22) and to always suppress a pressing force of the movable scroll (22) against the fixed scroll (21) through the high-pressure space (S2) in association with variation in compression ratio. More specifically, it will be preferable to suppress the pressing force to a large extent at high compression ratios while suppressing it to a small extent at low compression ratios.
In this construction, the pressing means (40) can have a structure that includes an oil groove (43) formed between contact surfaces of the fixed scroll (21) and the movable scroll (22) in contact with each other and a high-pressure oil introduction passage (44) for always introducing a high-pressure oil in the casing (10) into the oil groove (43).
Further, in this arrangement, the high-pressure space (S2) can be a high-pressure oil working space into which the high-pressure oil is supplied, and the high-pressure oil introduction passage (44) can be arranged to communicate from the high-pressure oil working space (S2) to the oil groove (43) and always guide the high-pressure oil in the high-pressure oil working space (S2) to the oil groove (43).
Furthermore, in the above arrangement, a frame (23) for dividing an inner space of the casing (10) into a low-pressure space (S1) and a high-pressure space (S3) can be disposed below the movable scroll (22), a sealing member (42) can be provided for dividing a space between the frame (23) and the movable scroll (22) into the low-pressure space (S1) and the high-pressure oil working space (S2), and the frame (23) can be provided with the high-pressure oil introduction passage (44).
Moreover, in each of the above arrangements, the high-pressure oil introduction passage (44) is preferably provided with a restriction section (44b).
Further, the restriction section (44b) can be constituted by a reduced-diameter part provided at least partially in the high-pressure oil introduction passage (44), constituted by a capillary tube (44e) provided at least partially in the high-pressure oil introduction passage (44), or formed so that a bar-like member (44f) narrower in diameter than the high-pressure oil introduction passage (44) is placed at least partially in the high-pressure oil introduction passage (44) to form a clearance with the high-pressure oil introduction passage (44).
(Operations)
In the above solutions, since the pressing force of the movable scroll (22) against the fixed scroll (21) is controlled in accordance with the variation in the compression ratio, the pressing force can be changed depending upon operating conditions.
Particularly in the arrangement wherein the pressing force of the movable scroll is suppressed when the compression ratio exceeds its predetermined value (approximately, for example, when the pressure differential between high and low pressures exceeds its predetermined value), if setting is made such that an appropriate pressing force can be obtained in the conditions where the compression ratio is equal to or less than the predetermined value, the movable scroll (22) can be held against upsetting by counteracting the gas compression-induced thrust load acting on the movable scroll (22) with the pressing force of the high-pressure space (S2) until the compression ratio (or any approximation such as the pressure differential between high and low pressures: same is true hereinafter) has reached the predetermined value. Further, when the compression ratio exceeds the predetermined value, suppressing the pressing force of the movable scroll (22) against the fixed scroll (21) can restrain the mechanical loss from increasing due to the excess of the pressing force.
Further, if the compressor is arranged to include an oil groove (43) between contact surfaces of the fixed scroll (21) and the movable scroll (22) in contact with each other and to introduce a high-pressure oil into the oil groove (43) when the compression ratio exceeds the predetermined value, the high-pressure oil provides a force acting in a direction to separate the movable scroll (22) away from the fixed scroll (21) so that the pressing force of the movable scroll (22) can be suppressed.
Furthermore, if the compressor is arranged to form the high-pressure space by a high-pressure oil working space (S2) and to guide the high-pressure oil in the high-pressure oil working space (S2) into the oil groove (43) when the compression ratio exceeds the predetermined value, at low compression ratios the pressure of the high-pressure oil presses the movable scroll (22) against the fixed scroll (21) to hold the movable scroll (22) against upsetting, while, upon excess of the compression ratio over the predetermined value, the pressure of the high-pressure oil is used to develop a force in a direction to separate the movable scroll (22) away from the fixed scroll (21) to restrain overpressing.
Moreover, if the high-pressure oil introduction passage (44) and the high-pressure oil introduction valve (45) for opening/closing the high-pressure oil introduction passage (44) are used as the high-pressure oil introducing means (46) for guiding the high-pressure oil into the oil groove (43), the high-pressure oil introduction valve (45) opens the high-pressure oil introduction passage (44) upon excess of the compression ratio over the predetermined value while closing it at the compression ratio equal to or less than the predetermined value. Thus, upset of the movable scroll (22) at low compression ratios and over-pressing thereof at high compression ratios can be prevented.
Further, the high-pressure oil introduction valve (45) has a structure that includes a cylinder (47) disposed to traverse the way of the high-pressure oil introduction passage (44) and a valve body (48) provided for reciprocation movement in the cylinder (47). In this manner, when the compression ratio exceeds the predetermined value, the valve body (48) is moved to its open position to open the high-pressure oil introduction passage (44) thereby preventing over-pressing of the movable scroll at high compression ratios. On the other hand, when the compression ratio is equal to or less than the predetermined value, the valve body (48) is moved to its closed position to block the high-pressure oil introduction passage (44) thereby preventing upset of the movable scroll (22) at low compression ratios.
Furthermore, if the cylinder (47) of the high-pressure oil introduction valve (45) has a structure that communicates at one end thereof with a low-pressure space (S1) provided in the casing (10) and communicates at the other end with a high-pressure space (S3) in the casing (10) and the valve body (48) is urged toward its closed position in the cylinder (47), when the compression ratio is equal to or less than the predetermined value so that the pressure differential between the low-pressure space (S1) and the high-pressure space (S3) is small, the urging force holds the valve body (48) at its closed position to prevent upset of the movable scroll (22). On the other hand, when the compression ratio exceeds the predetermined value so that the pressure differential is increased over a set point, the pressure differential moves the valve body (48) to the open position against the urging force to prevent over-pressing of the movable scroll (22).
Moreover, if the valve body (48) is formed at its outer periphery with a communication passage (48a) such as a circumferential channel and is arranged to block the high-pressure oil introduction passage (44) at its closed position while opening the high-pressure oil introduction passage (44) through the communication passage (48a) at its open position, when the valve body (48) is at its open position, the high-pressure oil introduction passage (44) can be opened through the communication passage (48a) to work the high-pressure oil in the oil groove (43) between the fixed scroll (21) and the movable scroll (22) thereby preventing over-pressing of the movable scroll (22).
Further, in the arrangement wherein the pressing force of the movable scroll is always suppressed in association with the variation in the compression ratio in the scroll compressor of the above predicated construction, if for example a high-pressure oil introduction passage (44) is provided for always introducing a high-pressure oil in the casing (10) into an oil groove (43) formed between contact surfaces of the fixed scroll (21) and the movable scroll (22) in contact with each other, the pressing force of the movable scroll (22) against the fixed scroll (21) is controlled in a manner for the high-pressure oil to always act on the oil groove (43).
In detail, when for example the high pressure rises so that the compression ratio becomes large, an oil with a higher pressure as compared with the case where the compression ratio is small acts on the oil groove (43). On the other hand, when for example the high pressure drops so that the compression ratio becomes small, an oil with a smaller pressure as compared with the case where the compression ratio is large acts on the oil groove (43). Therefore, the pressing force of the movable scroll (22) against the fixed scroll (21) is always controlled by using the high pressure (discharge pressure) that changes with the variation in the compression ratio. Accordingly, the pressing force is sufficiently suppressed at high compression ratios while the suppression is relieved at low compression ratios. This is substantially true for the consideration of the generic case including the variation in the low pressure. In this manner, the pressing force of the movable scroll (22) against the fixed scroll (21) is controlled in accordance with the variation in the compression ratio (pressure conditions) and thereby changes depending upon the operating conditions.
It is to be noted that if the compressor is set so that an appropriate counter-pressing force (a force in a direction to separate the movable scroll (22) away from the fixed scroll (21)) can be obtained, for example, in the conditions of low compression ratios, it can be supposed that when the compression ratio becomes high, the counter-pressing force will fail to some extent depending upon preset conditions such as the areas of the high-pressure space (S2) and the oil groove (43). In this case, since a counter-pressing effect itself is inevitably developed, the actual pressing force of the movable scroll (22) against the fixed scroll (21) can be suppressed with reliability as compared with the case where the high-pressure oil introduction passage (44) is not provided.
On the contrary, if the compressor is set so that an appropriate counter-pressing force can be obtained, for example, in the conditions of high compression ratios, it can be supposed that when the compression ratio becomes low, the counter-pressing force will be greater than required depending upon conditions so that the movable scroll (22) can be upset. In this case, however, if the restriction section (44b) for dimensionally controlling the clearance of the high-pressure oil introduction passage (44) by the reduced-diameter part (44b), the capillary tube (44e), the bar-like member (44f) or the like is provided, a pressure reduction effect is produced on an oil flowing through the high-pressure oil introduction passage (44) so that the counter-pressing force acting on the movable scroll (22) through the oil groove (43) can be reduced. As a result, even if the movable scroll (22) upsets, it can be recovered to its original un-upset position.
Further, if the high-pressure oil introduction passage (44) is provided with the restriction section (44b), it can be restrained so that the oil flows into the oil groove (43) upon upset of the movable scroll (22), thereby restricting oil leakage. As a result, there can be restrained the occurrence of a phenomenon of a decreased oil level resulting from oil inflow into the compression space (24) between both the scrolls (21, 22) and finally the occurrence of a phenomenon of oil shortage.
As can be seen from the above, in terms of practicality, oil leakage and decrease in operating efficiency due to upset of the movable scroll (22) can be suppressed to an extent that provides substantially no problem and leakage of refrigerant from the compression space (24) can be suppressed to the minimum.
Now, supposed that in the case where the high-pressure oil introduction passage (44) is provided with the high-pressure oil introduction valve (45) only without the restriction section (44b) and the high-pressure oil introduction valve (45) is actuated with the preset pressure differential between high and low pressures for the purpose of suppressing the pressing force of the movable scroll (22) against the fixed scroll (21) when the compression ratio exceeds the predetermined value, the high-pressure oil introduction valve (45) is set so as not to be actuated in the entire region (A2) including a slight margin beyond a region (A1) in which the upset can occur in FIG. 12 (an operating range diagram wherein the ordinate represents the high pressure and the abscissa represents the low pressure) which shows a working range of the scroll type compressor.
In this case, the inclination of a boundary line (a) of the upset region (A2) depends substantially upon the compression ratio (more specifically, also including the rotating speed or the like as conditions), while the inclination of a boundary line (b) for the working pressure of the high-pressure introduction valve (45) is based upon the pressure differential between high and low pressures. Therefore, both the inclinations of the boundary line (a) and boundary line (b) are normally unequal to each other. An over-pressing region (B2) in which the movable scroll (22) is not counter pressed will be thereby created to some extent in a region (B1) in which no upset originally occurs (in fact, a region also including (A2-A1)).
On the contrary, if the working pressure (see (b)) of the high-pressure oil introduction valve (45) is lowered as shown in FIG. 13, the over-pressing region (B2) can be reduced. At the time, there may occur an over-counter-pressing region (A3) by counter-pressing the movable scroll (22) within the upset region (A2) of the movable scroll (22). In this case, with the provision of the restriction section (44b) in the high-pressure oil introduction passage (44), even if the upset occurs in the over-counter-pressing region (A3), the high-pressure oil flowing through the high-pressure oil introduction passage (44) is reduced in pressure in the restriction section (44b) to decrease the counter-pressing force. Therefore, the upset can be immediately avoided.
Further, upon upset of the movable scroll (22), the restriction section (44b) of the high-pressure oil introduction passage (44) restrains oil inflow into the oil groove (43) and therefore oil leakage can be restricted. Accordingly, the occurrence of phenomena such as oil inflow into the compression space (24), drop in oil level and oil shortage can be suppressed. As can be understood from above, oil leakage and decrease in operating efficiency can be suppressed to an extent that provides substantially no problem in terms of practicality.
If the inclination of the boundary line (a) of the upset region (A2) and the inclination of the boundary line (b) for the working pressure of the high-pressure oil introduction valve (45) are set to substantially match each other both generally based on the compression ratio, the over-pressing region (B2) and the over-counter-pressing region (A3) themselves do not occur, which ensures further stable operation. Specifically, this is true for such a case that the high pressure and low pressure are detected, the compression ratio therebetween is operated and the highpressure oil introduction valve (45) is actuated in accordance with the compression ratio to control the pressing force of the movable scroll (22). (Effects)
As can be seen from the above, according to the above solutions, the pressing force of the movable scroll (22) against the fixed scroll (21) is controlled in accordance with the variation in the compression ratio thereby changing depending upon operating conditions.
In particular, if a gas compression-induced thrust load acting on the movable scroll (22) is counteracted by a pressing force slightly larger than required for anti-upsetting until the compression ratio (approximately, the pressure differential between high and low pressures: same is true hereinafter) has reached the predetermined value, the movable scroll (22) can be prevented from upsetting. Further, if the high pressure or the like is used to suppress the pressing force of the movable scroll (22) against the fixed scroll (21) when the compression ratio exceeds the predetermined value, it can be prevented that the pressing force becomes excessive to increase the mechanical loss.
As described above, according to the above construction, it can be prevented that at low compression ratios the pressing force fails so that the movable scroll (22) upsets and refrigerant leaks resulting in decreased efficiency, and at the same time it can be prevented that at high compression ratios the pressing force becomes excessive to produce an excessive mechanical loss. Therefore, efficient operation can be performed over the entire range from low compression ratio to high compression ratio.
Further, if the compressor is arranged so that an oil groove (43) is provided between contact surfaces of the fixed scroll (21) and the movable scroll (22) in contact with each other and a high-pressure oil is introduced into the oil groove (43), when the compression ratio exceeds the predetermined value, the high pressure in the compressor (1) is used to provide a force acting in a direction to separate the movable scroll (22) away from the fixed scroll (21). Accordingly, the pressure in the compressor (1) can be effectively used to prevent decrease in efficiency.
In particular, if the compressor is arranged so that the high-pressure space is a high-pressure oil working space (S2) and the high-pressure oil in the high-pressure oil working space (S2) is guided into the oil groove (43) when the compression ratio exceeds the predetermined value, the pressure of the high-pressure oil that was used to press the movable scroll (22) against the fixed scroll (21) until the compression ratio has exceeded the predetermined value can be used to develop a force in a direction to separate the movable scroll (22) away from the fixed scroll (21) upon excess of the compression ratio over the predetermined value. Accordingly, the pressure in the compressor (1) can be used more effectively.
Further, if the high-pressure oil introduction passage (44) and the high-pressure oil introduction valve (45) for opening/closing the high-pressure oil introduction passage (44) are used as the high-pressure oil introducing means (46) for guiding the high-pressure oil into the oil groove (43), and the high-pressure oil introduction valve (45) opens the high-pressure oil introduction passage (44) upon excess of the compression ratio over the predetermined value while closing it at the compression ratio equal to or less than the predetermined value, upset of the movable scroll at low compression ratios and over-pressing thereof at high compression ratios can be prevented and the construction can be prevented from being complicated.
In particular, if the high-pressure oil introduction valve (45) has a structure that includes a cylinder (47) disposed to traverse the way of the high-pressure oil introduction passage (44) and a valve body (48) provided for reciprocation movement in the cylinder (47) and the valve body (48) is allowed to move to its open or closed position in accordance with the compression ratio, the arrangement wherein the high-pressure oil introduction passage (44) is opened/closed to prevent over-pressing of the movable scroll (22) at high compression ratios and upset of the movable scroll (22) at low compression ratios can be concretely and easily implemented.
In this case, if the cylinder (47) is arranged to communicate at one end thereof with a low-pressure space (S1) in the casing (10) and communicate at the other end with a high-pressure space (S3) in the casing (10) and the valve body (48) is urged toward the closed position in the cylinder (47), when the urging force and the pressure differential with which the high-pressure oil introduction valve (45) is actuated are set at respective suitable values, movement of the valve body (48) in accordance with the variation in the compression ratio can be ensured in a simple structure.
Further, if the valve body (48) is formed in its outer periphery with a communication passage (48a) such as a circumferential channel and is arranged to open/close the high-pressure oil introduction passage (44) using the communication passage (48a), the construction can be further simplified.
Furthermore, the compressor has a structure in which a frame (23) for dividing an inner space of the casing (10) into a low-pressure space (S1) and a high-pressure space (S3) is disposed below the movable scroll (22), a sealing member (42) is provided for dividing a space located between the frame (23) and the movable scroll (22) into the low-pressure space (S1) and a high-pressure oil working space (S2), and the frame (23) is provided with the high-pressure oil introduction passage (44) and the high-pressure oil introduction valve (45). In this case, the arrangement wherein the high-pressure oil introduction valve (45) is actuated with the pressure differential between high and low pressures in accordance with the variation in the compression ratio can be easily implemented.
Moreover, in the arrangement wherein the pressing force of the movable scroll is always suppressed by the pressing means (40) in association with the variation in the compression ratio, when for example a high-pressure oil introduction passage (44) is provided for always introducing the high-pressure oil in the casing (10), as mentioned above, into the oil groove (43) formed between contact surfaces of the fixed scroll (21) and the movable scroll (22) in contact with each other, the pressing force of the movable scroll (22) against the fixed scroll (21) can be suppressed at high compression ratios while the suppression can be relieved at low compression ratios. In this manner, since the pressing force of the movable scroll (22) against the fixed scroll (21) is controlled in accordance with the variation in the compression ratio with the change in the operating condition, the compressor can be operated over the entire range from low compression ratio to high compression ratio with higher efficiency than the prior art.
Further, even if the counter-pressing force fails to some extent at high compression ratios, a counter-pressing effect itself is inevitably developed. Therefore, the pressing force of the movable scroll (22) against the fixed scroll (21) can be suppressed at high compression ratios with higher reliability than the prior art thereby providing increased efficiency.
On the contrary, when the compressor has a structure that includes a restriction section (44b) in the high-pressure oil introduction passage (44), even if the movable scroll (22) is upset in the conditions of low compression ratios, the high-pressure oil is reduced in pressure and the suppression of the pressing force is relieved so that the movable scroll (22) can be recovered from the upset position and leakage of oil and refrigerant can be suppressed. Accordingly, there seldom arises a problem of deterioration in efficiency in practice, which enables the operation to be stabled.
Further, if both the high-pressure oil introduction valve (45) and the restriction section (44b) for reducing the pressure of the high-pressure oil are provided in the high-pressure oil introduction passage (44), oil inflow into the compression space (24), drop in oil level and oil shortage can be suppressed even if the upset occurs in the over-counter-pressing region (A3). And, upon upset of the movable scroll (22), the high-pressure oil flowing through the high-pressure oil introduction passage (44) is reduced in pressure in the restriction section (44b) and then guided into the oil groove (43). Therefore, the counter-pressing force is decreased so that the movable scroll is immediately recovered from the upset position. Furthermore, since the over-pressing region (B2) can be reduced, this provides further stable operation over the entire range from low compression ratio to high compression ratio.
When the arrangement wherein the high-pressure oil introduction valve (45) is provided uses the pressure differential between high and low pressures to actuate the valve, it is difficult to control the pressing force in complete accordance with the variation in the compression ratio. However, depending upon conditions such as setting of the working pressure of the valve, the pressing force can be controlled substantially in accordance with the variation in the compression ratio.
Further, the description mentioned so far has been made with reference to the variation in the compression ratio with the variation in the high pressure. Substantially the same operations and effects can also be exhibited for consideration of the generic case including the variation in the low pressure.